JP5368970B2 - Method and apparatus for drying honeycomb molded body - Google Patents

Description

  The present invention relates to a drying method and a drying apparatus for a honeycomb formed body that is an unfired body of a honeycomb structure.

  Honeycomb structures are widely used for catalyst carriers, various filters, and the like. Recently, it has attracted attention as a diesel particulate filter (DPF) for capturing particulate matter discharged from a diesel engine.

  In general, the honeycomb structure is mainly composed of ceramics. To manufacture such a honeycomb structure, first, water and various additives such as a binder are added to a ceramic raw material to form a clay, and then extruded to form a honeycomb-shaped formed body (honeycomb forming). Body). If the honeycomb formed body is dried and then fired, a honeycomb structure can be manufactured.

  As a drying method of the honeycomb molded body, it is generated by a dielectric drying method using a high-frequency energy generated by passing an electric current between electrodes provided above and below the honeycomb molded body, or by a gas burner. A hot air drying method is known in which drying is carried out by introducing hot air that has been generated. However, recently, instead of these drying methods, or in combination with these drying methods, a drying method using microwaves (microwave drying method) having advantages such as a high drying speed has come to be performed. (For example, see Patent Documents 1 to 3).

  However, in such a microwave drying method, drying of the upper and lower ends and the outer peripheral portion of the honeycomb formed body is delayed from other parts in the drying process, and it is sometimes difficult to dry the entire honeycomb formed body at a uniform speed. there were. Since the honeycomb formed body shrinks due to evaporation of moisture, if the drying speed is not uniform, problems such as deformation and breakage are likely to occur. Furthermore, the partition walls (ribs) partitioning the cells are becoming thinner, and the honeycomb molded body with thinner partition walls is more likely to be deformed. Therefore, uniform drying speed has become a particularly important issue in recent years.

JP 2002-283329 A JP 2002-283330 A International Publication No. 2005/023503 Pamphlet

  The present invention has been made in view of such problems of the prior art, and the problem is that a honeycomb molded body can be formed in a shorter time while suppressing the occurrence of defects such as deformation and breakage. An object of the present invention is to provide a drying method and a drying apparatus for a honeycomb formed body that can be dried.

According to the present invention, there is provided a method for drying an unfired honeycomb formed body having a plurality of cells serving as fluid flow paths partitioned by partition walls, which is made of a raw material composition containing a ceramic raw material, water, and a binder. Then, superheated steam whose temperature is adjusted to a wet bulb temperature of 70 ° C. or higher, or a mixed gas of steam and heated air is rectified, and the entire honeycomb formed body is heated at a temperature of 115 ° C. or higher and 300 ° C. or lower. There is provided a method for drying a honeycomb formed body in which the honeycomb formed body is dried by passing the cells uniformly .

  In the present invention, it is preferable that the binder is a binder material having thermal gelation characteristics or thermosetting characteristics.

In addition, according to the present invention, a steam supply unit that supplies superheated steam, a buffer chamber that rectifies superheated steam supplied from the steam supply unit, and a honeycomb formed body are provided above the buffer chamber. An upper chamber for passing the superheated steam through the honeycomb molded body, a hood portion for collecting the superheated steam that has passed through the honeycomb molded body, and a workpiece mounting plate . The superheated steam is introduced laterally from the side to the buffer chamber, is caused to collide with the inner inner wall of the buffer chamber, and rises in the buffer chamber. is configured, the workpiece mounting plate, the is configured to have the same cell density and the honeycomb molded body, vertical Drying apparatus honeycomb molded body is provided.

  In the present invention, the honeycomb formed body can be dried in a shorter time while suppressing the occurrence of defects such as deformation and breakage.

FIG. 3 is a perspective view showing an example of a honeycomb molded body used in the method for drying a honeycomb molded body according to the present invention. FIG. 6 is a perspective view showing another example of a honeycomb formed body used in the method for drying a honeycomb formed body according to the present invention. 1 is a schematic view showing an embodiment of a drying apparatus for a honeycomb formed body according to the present invention. It is a top view which shows an example of a workpiece | work mounting board. 4 is a graph showing a temperature change with respect to a drying time of a honeycomb formed body in Example 1. FIG. 6 is a graph showing a temperature change with respect to a drying time of a honeycomb formed body in Example 2. FIG. 4 is a graph showing a temperature change with respect to a drying time of a honeycomb formed body in Comparative Example 1. FIG. It is a graph which shows the flow rate distribution of superheated steam in the case of no buffer chamber. It is a graph which shows the flow rate distribution of superheated steam in the case of having a buffer chamber. It is explanatory drawing which shows the measuring point of the flow rate of the superheated steam in a honeycomb molded object.

Explanation of symbols

1: honeycomb formed body, 2: partition wall, 3: cell, 4 : outer peripheral wall, 10: drying device, 12: steam supply unit, 14: buffer chamber, 16: upper chamber, 18: honeycomb formed body, 20: hood unit 22: Workpiece mounting plate.

  BEST MODE FOR CARRYING OUT THE INVENTION The best mode for carrying out the present invention will be described below, but the present invention is not limited to the following embodiment, and is based on the ordinary knowledge of those skilled in the art without departing from the gist of the present invention. It should be understood that modifications and improvements as appropriate to the following embodiments also fall within the scope of the present invention.

  In the method for drying a honeycomb formed body of the present invention, the honeycomb formed body is dried by passing superheated steam whose temperature is adjusted to a wet bulb temperature of 70 ° C. or higher through the cells of the honeycomb formed body. It is a characteristic. The details will be described below.

In the drying method of the present invention, the honeycomb formed body to be dried has a structure as shown in FIGS. 1 and 2, for example. That is, the honeycomb formed body 1 has a plurality of cells 3 that serve as fluid flow paths partitioned by the partition walls 2. Moreover, the honeycomb formed body 1 is usually configured by disposing an outer peripheral wall 4 so as to surround a plurality of cells 3. The cross-sectional shape orthogonal to the axial direction (flow channel direction) of the cell 3 is not limited, and a shape such as a quadrangle as shown in FIG. 1 or a circle as shown in FIG. 2 can be arbitrarily selected. it can.

  The honeycomb formed body is an unfired body constituted by a raw material composition containing a ceramic raw material, water, and a binder. Examples of the ceramic raw material include oxide ceramics such as alumina, mullite, zirconia, and cordierite; non-oxide ceramics such as silicon carbide, silicon nitride, and aluminum nitride. A silicon carbide / metal silicon composite material, a silicon carbide / graphite composite material, or the like can also be used.

  Examples of the binder having thermal gelation characteristics or thermosetting characteristics contained in the ceramic molded body that is the subject of the present invention include methyl cellulose, hydroxypropyl methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, and hydroxyethyl methyl cellulose. Of these, methylcellulose is most commonly used. The gelation temperature of these gelling binders varies depending on the type, but is about 50 to 80 ° C., for example, about 55 ° C. in the case of methylcellulose. It is also possible to mix different types of gelling binders.

  In drying the honeycomb formed body having the above-described configuration, in the present invention, superheated steam whose temperature is adjusted so that the wet bulb temperature is 70 ° C. or higher, or a mixed gas of steam and heated air is used. The wet bulb temperature of the superheated steam or the mixed gas of steam and heated air is preferably 70 to 100 ° C, more preferably 80 to 100 ° C. When the wet bulb temperature of the superheated steam or the mixed gas of steam and heated air is less than 70 ° C., the thermal gelation of the binder is insufficient, the honeycomb formed body is deformed greatly when it is dried, and is cut at the end face to cause breakage. The optimum wet bulb temperature of the water vapor or the mixed gas of water vapor and heated air is not unambiguous, and should be changed depending on the type of ceramic and the type of binder.

  As temperature of the superheated steam which passes a cell, or the mixed gas of water vapor | steam and heated air, 60 to 300 degreeC or less is preferable, More preferably, it is 70 to 200 degreeC. When the temperature of the superheated water vapor that passes through the cells is less than 60 ° C., the honeycomb formed body is heated, but vapor is condensed and the honeycomb formed body absorbs moisture and swells easily, resulting in problems such as shape deformation. On the other hand, if it exceeds 300 ° C., the binder material is removed, and the honeycomb formed body becomes brittle and easily deforms or breaks. The optimum temperature of the superheated steam is not unambiguous and should be changed according to the type of ceramic and the type of binder.

  The time required for the superheated steam to pass through the cells, that is, the time required for the water content of the honeycomb formed body to be in an equilibrium state varies depending on the shape, moisture, dimensions, steam temperature, humidity, etc. of the honeycomb formed body. ˜120 minutes, preferably about 10 to 60 minutes. If the time for allowing the superheated steam to pass through the cell is too short, it may not be in a sufficient equilibrium state. The optimum temperature time for passing the superheated steam through the cell is not unique, and should be changed according to the ceramic type, shape, moisture, dimensions, etc., and the temperature and humidity of the steam to be passed.

  FIG. 3 is a schematic view showing an embodiment of a drying apparatus for a honeycomb formed body according to the present invention. The drying apparatus 10 includes a steam supply unit 12 that supplies superheated steam A, a buffer chamber 14 that rectifies superheated steam A supplied from the steam supply unit 12, and a buffer formed body 18 above the buffer chamber 14. Are provided with an upper chamber 16 and a hood portion 20 in which the superheated steam A that has passed through the honeycomb formed body 18 is recovered.

  In the drying apparatus 10, superheated steam A is supplied from the steam supply unit 12 to the buffer chamber 14. Here, the superheated steam A is introduced laterally from the side with respect to the buffer chamber 14 and is made to collide with the inner side wall of the buffer chamber 14, and then the superheated steam A rises in the buffer chamber 14. As described above, the superheated steam A is rectified by colliding with the inner side wall of the buffer chamber 14, and the superheated steam A rises in the entire buffer chamber 14 at a substantially uniform speed.

  The superheated steam A rectified in the buffer chamber 14 rises in the buffer chamber 14 and then enters an upper chamber 16 provided above the buffer chamber 14. Inside the upper chamber 16, a honeycomb formed body 18 placed on the work placing plate 22 is disposed, and the superheated steam A passes almost uniformly through all the cells of the honeycomb formed body 18, and the honeycomb formed body 18 is dried almost evenly. As shown in FIG. 4, the workpiece mounting plate 22 is configured to have the same cell density as that of the honeycomb formed body 18, so that the superheated steam A is uniformly distributed in all the cells of the honeycomb formed body 18. Preferred for passing through.

  Next, the superheated steam A that has passed through the cells of the honeycomb formed body 18 enters the hood portion 20 disposed in the upper portion of the upper chamber 16 and is collected.

  The cell density, partition wall thickness, cell shape, dimensions, etc. of the honeycomb molded body that is the subject of the drying method of the present invention are not particularly limited. However, a honeycomb molded body with thin partition walls (for example, partition wall thickness: 150 μm or less) that is more likely to be deformed or the like, or a large-sized honeycomb molded body (for example, total channel length: 200) that is likely to have a difference in drying speed at each portion. ˜1000 mm, outer diameter: 150 to 600 mm) is particularly effective.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples.

(Examples 1-2, Comparative Example 1)
A honeycomb molded body produced by using a forming aid of methylcellulose (MC) as a binder to a cordierite oxide ceramic raw material and a silicon carbide nonoxide ceramic raw material having an outer shape as shown in FIG. Ceramic body: Outer diameter × channel length: 106 mmφ × 220 mm, number of cells: 93 cells / cm ² , partition wall thickness: 64 μm) (silicon carbide-based non-oxide ceramic molded body: outer diameter × channel length: 35 mm) (Section is square) × 330 mm, number of cells: 31 cells / cm ² , partition wall thickness: 381 μm)]. With respect to the prepared honeycomb formed body, the drying apparatus 10 having the configuration shown in FIG. 3 is used, and the water vapor amount is 50 kg / hr for the cordierite-based material, while 20 kg / hr for the silicon carbide-based material. , Mixed with superheated steam and hot air at 100 ° C to 120 ° C, and adjusted the tact time of each material to 20 minutes or less with a mixed gas whose wet bulb temperature was adjusted to 60 ° C, 70 ° C, 80 ° C and dried. Went. Note that the dimensions of the buffer chamber 14 and the upper chamber 16 in the drying apparatus 10 are outer diameter × flow path length: 440 mmφ × 700 mm and 420 mmφ × 800 mm, respectively. As the work mounting plate 22, one having the same cell density as that of the honeycomb formed body was used.

(Drying conditions)
Example 1: Hot air temperature 115 ° C
Humidity 27%
Wet bulb temperature 70 ° C
Example 2: Hot air temperature 125 ° C
Humidity 40%
Wet bulb temperature 80 ℃
Comparative Example 1: Hot air temperature 100 ° C
Humidity 20%
Wet bulb temperature 60 ° C

  FIG. 5 (Example 1), FIG. 6 (Example 2), and FIG. 7 (Comparative Example 1) show temperature changes with respect to the drying time of the honeycomb formed body (carrier). As shown in FIGS. 5 to 7, the carrier temperature during drying coincides with the superheated steam or the wet bulb temperature of the mixed gas of steam and heated air, and the superheated steam starts from the location where the moisture of the carrier has reached an equilibrium state. It can also be seen that the temperature of the mixed gas of water vapor and heated air has been reached. In Example 1, the deformation of the honeycomb formed body was small and no breakage occurred, and in Example 2, neither deformation nor breakage of the honeycomb formed body occurred. On the other hand, in Comparative Example 1, the honeycomb molded body was greatly deformed, and the end face was cut.

(Example 3, Comparative Example 2)
A confirmation experiment was conducted on the effect of the buffer chamber. That is, in the drying apparatus 10 used in Examples 1 and 2, the flow velocity distribution of superheated steam inside the cells of the honeycomb formed body with and without the buffer chamber 14 was measured and compared. The results are shown in FIGS. FIG. 10 shows measurement points of the flow rate of superheated steam in the honeycomb formed body.

  As can be seen from FIGS. 8 and 9, when there is no buffer chamber, the flow rate of superheated steam inside the cells of the honeycomb molded body varies greatly, and when the buffer chamber is provided, the flow rate of superheated steam inside the cells of the honeycomb formed body is It was uniform. And by making the flow rate of superheated steam inside the cells of the honeycomb formed body uniform, the dry distribution in the radial direction of the honeycomb formed body was reduced.

  According to the method and apparatus for drying a honeycomb formed body of the present invention, a honeycomb formed body that is an unfired body of a honeycomb structure widely used for a catalyst carrier, various filters such as DPF, etc. is suitably dried. Can do.

Claims (3)

A method of drying an unfired honeycomb formed body having a plurality of cells serving as fluid flow paths partitioned by partition walls, comprising a raw material composition containing a ceramic raw material, water, and a binder,
The superheated steam or the mixed gas of steam and heated air whose temperature is adjusted so that the wet bulb temperature becomes 70 ° C. or higher is rectified, and the temperature is 115 ° C. or higher and 300 ° C. or lower in all cells of the honeycomb molded body. A method for drying a honeycomb formed body, wherein the honeycomb formed body is dried by passing the water uniformly through.   The method for drying a honeycomb formed body according to claim 1, wherein the binder has thermal gelation characteristics or thermosetting characteristics. A steam supply section for supplying superheated steam;
A buffer chamber for rectifying superheated steam supplied from the steam supply unit;
An upper chamber provided above the buffer chamber for disposing a honeycomb formed body, and passing through the superheated steam through the honeycomb formed body;
A hood portion for collecting the superheated steam that has passed through the honeycomb formed body ;
A workpiece mounting plate and <br/>
In the steam supply unit and the buffer chamber, the superheated steam is introduced laterally from the side with respect to the buffer chamber, is caused to collide with an inner inner wall of the buffer chamber, and rises in the buffer chamber. Configured,
The workpiece mounting plate is configured to have the same cell density as the honeycomb formed body,
A device for drying a vertical honeycomb molded body.

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